handle allocation error. Found by Klockwork (www.klocwork.com)

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@8485 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/applications/mod_dptools/mod_dptools.c

@@ -1852,6 +1852,8 @@ static switch_call_cause_t user_outgoing_channel(switch_core_session_t *session,
 
 	user = strdup(outbound_profile->destination_number);
 
+	if (!user) goto done;
+
 	if (!(domain = strchr(user, '@'))) {
 		goto done;
 	}